The present invention is drawn to a method and apparatus for retrofitting a round or cylindrical shaped door knob with a lever type handle.
In the past numerous door knobs have been employed which require a person to grip the knob by hand and rotate the knob clockwise or counter-clockwise to operate the knob and lock mechanism. While the door knobs operate in an apparent simple and easy manner, in many cases handicapped persons may lack the ability to grip and rotate such a knob. Accordingly it has become desirable to replace or retrofit the cylindrical or ball shaped door knob with a lever type handle which is more easily actuated by all including the handicapped.
The prior art is replete with devices for adapting conventional door knobs to lever type handles. For example, U.S. Pat. No. 4,397,489 discloses an adapter for providing a lever attachment to a round door knob which has a hollow threaded cylinder fitted with a lever which cylinder slides over the knob and is frictionally secured to the knob by compressing the knob between one end of the cylinder and a tightened split ring threaded into the other end of the cylinder. Elastomeric material placed on either or both sides of the knob increase the friction and prevent slipping of the adapter on the knob after tightening. This adapter is extremely complex in structure due to its numerous parts. In addition, the door knob and shank must be disassembled from the door lock system in order to secure the device to the knob. Both of these disadvantages render the device unsuitable for commercial use. U.S. Pat. No. 4,223,931 discloses a device for converting a door knob to a lever operated door knob wherein the device comprises a mounting portion for mounting the operating lever to a doorknob; a lever secured to the mounting portion; the mounting portion being secured to the back face of a conventional door knob; and the mounting portion partially surrounding the stem of the doorknob. Again the door knob must be removed from the door unit to retrofit same. U.S. Pat. No. 4,648,643 discloses a multi-piece retrofit lever assembly which comprises a lever assembly of two principal parts: a lever with a circular aperture to engage the shank of a door knob, and a retaining plate, for fastening thereof to the lever, having a projecting cog. The cog engages a knob catch slot in the door knob shank. Accordingly, as the lever is rotated/manipulated, it turns the door knob through the engagement of the cog with the slot, and the fastening of the plate to the lever. The assembly accommodates retrofitting thereof to doors having round door knobs. Again, this assembly is complex in structure, expensive to produce and difficult to retrofit.
Naturally, it would be highly desirable to provide a retrofit device for converting a round door knob to a lever action door knob which is readily assembled onto a door knob in situ on the door.
Accordingly, it is the principle object of the present invention to provide a device for adapting a round door knob to a lever handle door knob which is of simple, economic construction and easily assembled to the round door knob without removing the door knob from the door.
It is a particular object of the present invention to provided a method for retrofitting a round door knob with a lever assembly which insures secure fit.
It is a still further object of the present invention to provide a lever handle door knob attachment which meets local fire code requirements and is aesthetically pleasing.
Further objects and advantages of the present invention will appear hereinbelow.